A fuel cell is an electrochemical device that utilizes a fuel (hydrogen) that is combined with oxygen to produce electric power, water, and heat. Importantly, there are no combustion processes taking place, so emissions such as CO2 and NOX are eliminated. Further, fuel cells are particularly efficient compared to combustion engines.
No matter what type, Solid Oxide, Proton Exchange Membrane (PEM), etc., all fuel cells have the same basic constituents: the anode, the electrolyte and the cathode. The anode is in contact with the hydrogen fuel and the cathode is in contact with the oxidant. As the fuel cell""s reverse electrolysis takes place through the electrolyte wherein electric power is produced, water is formed on the surface of the cathode as oxygen combines with the ionized hydrogen (protons) that cross the electrolyte. The entire assembly also becomes heated due to the exothermal chemical process as it creates electricity.
Conventional fuel cells are static devices wherein numerous anode/electrolyte/cathode cells are connected, generally in series, because the voltage produced by each fuel cell element is low, about a volt. Each fuel cell stack element is about 0.1 inches thick and, typically 5 to 10 inches square. Within each of these stack elements are various structural components that facilitate the supply of air (oxygen) and hydrogen as well as means to circulate cooling water within the fuel cell stack and remove water formed during operation.
The present invention reveals a new type of fuel cell configuration that offers many attributes, especially in association with PEM fuel cells At its core, the rotating fuel cell, as its name implies, is a dynamic stack of fuel cell elements, called PEM xe2x80x9cbladesxe2x80x9d hereinafter, that rotate within the surrounding air (oxidant stream) This dynamic fuel cell configuration has numerous advantages:
Direct cathode exposure to the ambient air at a relative slow velocity, dissipates fuel cell waste heat readily; conventional fuel cell stack require complex internal water-cooling systems. The present invention simply transfers the heat directly to the ambient (or pressurized) air (much as in an air cooled engine) and not only eliminates the internal stack cooling system, but also eliminates the entire heat transfer system required to reject the heat gathered in the stack.
The centrifugal force that arises due to the rotation of the fuel cell assembly readily rids the cathode of the accumulation of water that occurs to produce electricity (and heat). Keeping the exposed cathode surface free of water (xe2x80x9cslinging it awayxe2x80x9d) improves the performance of the fuel cell because the surrounding air (oxygen) is always in contact with the cathode; the presence of liquid water gets in the way of air.
Because the fuel cell blades of the rotating fuel cells are constantly in contact with new and turbulent air, the cathodic surface oxygen concentration will always be maximized.
Perhaps most important, the fuel cell blades can be arranged in a fashion such that the rotating fuel cell assembly causes its own aspiration (much like a fan).
The present invention, in broad terms, provides a rotating fuel cell comprising a housing means having bearing means which define a longitudinally-extending rotary axis. The fuel cell further includes an elongated shaft rotatably supported on the bearing means; the shaft has a hollow bore extending from one end thereof to a preselected length. The shaft further has a radially-extending port connecting the hollow bore to the outer surface of the shaft. A radially-extending PEM fuel cell assembly is positioned on the shaft to rotate therewith. The PEM fuel cell assembly has a gas passage therein which is in register with the port of the shaft. Means are provided for supplying hydrogen gas to the hollow bore of the shaft. Air (oxygen) is supplied to the exterior of the PEM fuel cell assembly. Motor means are connected to one end of the shaft and is adapted to rotate the shaft and the PEM fuel cell assembly about the axis in the oxidant. Electrical output means are connected to the PEM fuel cell assembly, e.g., slip rings, rotating transformer, etc.).
In a preferred embodiment of the invention depicted in the drawings, a plurality of radially-extending PEM fuel cell assemblies are arranged in a stack and positioned on the shaft in side-by-side longitudinally-spaced-apart relationship; each of the assemblies having a gas passageway in register with one of a plurality of radially-extending and longitudinally-spaced-apart ports in the shaft. In all embodiments, the PEM fuel cell assemblies comprise a blade which is adapted, when rotated, to cause air, i.e., oxidant, to flow longitudinally against and around the assembly(ies). Also in the preferred embodiment, the shaft is electrically conductive and insulative means are positioned between the outer periphery of the shaft and the plurality of PEM assemblies. The PEM assemblies are electrically connected in series relationship to produce a total output voltage which is a function of the multiple of the output voltage of one assembly.